This invention pertains to novel 2,6-dinitrophenyl seleninic acids, selenium halides and diselenides. More particularly, this invention relates to a process for utilizing these novel selenium compounds to catalyze the epoxidation of olefins.
Epoxides are utilized in the chemical industry as intermediates in the preparation of urethanes, glycol solvents, coating compositions, surfactants, plasticizers and many other products. The most widely employed commercial procedure for preparing epoxides involves the oxidation of a double bond with chlorine to form the chlorohydrin, followed by a base-promoted ring closure to form the epoxide. The principal disadvantage of this process is the simultaneous production of a stoichiometric quantity of a chloride salt as the by-product.
A silver-based catalyst can be utilized with molecular oxygen to epoxidize ethylene in the vapor phase. However, this technique is not generally applicable to substituted olefins due to a lack of selectivity and the formation of by-products.
U.S. Pat. No. 3,351,635 discloses a two-step process in which a hydrocarbon, such as isopropyl benzene or isobutane, is first oxidized by air to the corresponding hydroperoxide. The hydroperoxide intermediate is then reacted with the olefin in the presence of vanadium, molybdenum or tungsten. However, this process suffers from the disadvantage that a stoichiometric amount of alcohol is generated along with the epoxide.
The use of a variety of organometallic compounds as catalysts for epoxidation of olefins with hydrogen peroxide has been taught. U.S. Pat. Nos. 3,993,673 and 3,953,480 disclose the use of organometallic catalysts of lead, antimony, bismuth and arsenic. However, these organometallic catalysts are not completely satisfactory, because they do not exhibit sustained, high catalytic activity.